Method for the surface treatment of glass



March 4, 1969 H. J. CHAUMONT 3,430,399

METHOD FOR THE SURFACE TREATMENT OF GLASS Filed June 29, 1965 Sheet of 2 3mm f/EMQ/ JULES [/mwm/W 5M d m March 4, 1969 H. J. CHAUMONT METHOD FOR THE SURFACE TREATMENT OF GLASS Sheet Filed June 29, 1965 m e w United States Patent US. Cl. 51--283 Int. Cl. B241) 1/00, 7/00, 9/00 2 Claims ABSTRACT OF THE DISCLOSURE Method for grinding and polishing sheet glass. A rubhing block is driven in an orbital path by novel linkage which applies to the block a force inclined to the rubbing surface and which passes through a point between the inertia center of the block and the projection of that center on the rubbing surface. As a result deleterious effects of rapidly reversing component forces otherwise tending to tilt the block in planes normal to the rubbing surface, are obviated. The linkage also acts automatically to create and apply to the rubbing block, a vertical component force equal and opposite at each instant to the vertical component of the inclined force, so that effective pressure of the block upon the glass is uniform over its area.

This invention relates to the grinding and polishing of sheet glass and, more particularly, to a method wherein the surfacing of the glass is effected by the orbital or translatory movement of a pad or pads over the surface of the work, in conjunction with interposed grinding or polishing compounds.

The forces applied to the surfacing pad to move it in its orbital or other path are necessarily applied at some distance above the surface of the sheet of glass being worked and are, of course, parallel to this surface. Heavy pressure is applied to the pad and as the result of frictional resistance of the pad in contact with the sheet, together with forces necessary to overcome inertia of the pad, its mounting frame and parts moving therewith, couples are created which tend to tilt the pad out of its desired plane parallel with the sheet. Such couples are undesirable and deleterious not only because they tend to set up vibrations of the pad and its carrying frame, but also because any wear or looseness of the hearings or pivot joints can result in actual tilting of the pad. This tilting, while actually small in practice, results in unsatisfactory erformance of the machine and an uneven or wavy final surface of the sheet of glass, and which may detract from its quality.

It is an object of the invention to provide a mechanism of the type under discussion, which obviates the drawbacks stated in the preceding paragraph.

More specifically it is the chief object of the invention to provide a link connecting each drive mechanism with its polishing or grinding pad, which is inclined at an angle to the plane of the pad or, what is the same thing, to the plane of the sheet of glass, such that the axis of the link extended, lies in a plane normal to the plane of the pad and passes between two closely vertically spaced points one of which is the centroid of the pad, its frame and part moving therewith, and the other is the point of application of the resultant of all frictional and inertia orces due to the surfacing motion.

The force transmitted by the aforesaid link, being inclined to the surface of the glass, has a vertical component which, of course, varies with the force required to effect the orbital or other movement of the pad over and relatively to the sheet of glass. This component is 3,430,399 Patented Mar. 4, 1969 undesirable and prejudicial to the production of a perfect finished surface upon the sheet because it results in continuous variation in the pressure of the pad upon the sheet.

It is therefore a further object of the invention to provide a linkage and lever system between the force-applying mechanism and the frame of the polishing pad, which consists essentially of two levers so constructed, arranged and interconnected as to create a force eflective upon the pad or the frame thereof, which is at each instant equal and opposite to the aforesaid undesired vertical force component.

It is another object to provide a system as aforesaid wherein the resultant of forces developed and applied to move the pad in a first direction, lie in a first plane normal to the surface of the sheet and containing the axis of the aforesaid link, while the resultant of other forces required to assure the desired orbital or other motion of the pad, are applied in a second plane normal to the aforesaid first plane and to the surface of the sheet of glass. These two resultant forces combine to produce at each instant the desired movement of the pad.

Still another object is to provide a surfacing mechanism of the type mentioned, wherein the power required to effect movement of the pad is provided by two spaced power-driven elements or blocks and to which identical synchronous motions are imparted.

The manner and mechanism by which the aforesaid and other objects and advantages are attained, will be understood by those skilled in the art, after a study of the following detailed description in connection with the accompanying drawing of one embodiment of the invention, which is to be taken in a purely illustrative rather than a limiting sense.

In the drawing:

FIGURE 1 is a perspective view of mechanism embodying the invention;

FIGURE 2 is a detail plan view of one of the two levers forming a part of the assemblage;

FIGURE 3 is a detail plan view of the second lever forming a part of the assemblage;

FIGURE 4 is a perspective view of the lower surface and appendages of one of the two identical power-driven blocks of FIGURE 1; and

FIGURE 5 is a diagrammatic side elevational view of one of the two link-lever assemblies, with a diagram of forces superposed thereon.

Referring in detail to FIGURE 1, 1 and 1 identify blocks which are positioned substantially coplanar and in spaced adjacent relation. Block 1 has the cranked end of a shaft 17 connected centrally thereto by antifriction bearing 18. Likewise block 1' has the cranked end of a shaft 17 journaled centrally therein by antifriction bearing 18. The two cranks have equal throws and the shafts are connected by means not shown for rotation in synchronism. Such means may take the form of gearing, chain and sprockets, or equivalent mechanism.

The frame to which the polishing or grinding pad is secured is identified at 2 and is shown by way of example as rectangular in plan. It will be understood that the pad is attached to frame 2, to the face thereof which faces downwardly in FIGURE 1.

First and second bearing brackets 7, 7' are fixed with frame 2 at one side edge thereof, each adjacent a respective end of the edge. A third bracket 16 is fixed to the frame centrally thereof.

One end of inclined link 4 is pivoted in bracket 7. The other end of this link is pivotally connected at 19 between the contiguous arms at one end of an open-center generally O-shaped lever 5. The other end of this lever is pivotally connected at 20 to one end of a relatively short link 8. In normal operation lever will lie in a plane substantially parallel with the plane of frame 2 and the sheet of glass 3, FIGURE 5. At the same time, link 8 may be substantially normal to the plane of frame 2.

Frame 2 has a pair of bearing lugs 21, 21 fixed to and upstanding from its upper surface as seen upon FIGURE 1. These lugs are positioned in the longitudinal center line of the frame, each directly opposite a respective one of the bearing brackets 7, 7'. Confining attention to the left link assembly as shown upon FIGURE 1, a horizontal lever 6 has one end pivotally attached to hearing lug 21 and its other end pivotally connected with the lower end of vertical link 8. FIGURE 2 shows lever 5 in plan and FIGURE 3 similarly depicts lever 6.

As clearly shown upon FIGURE 1, block 1 has a notch 22 in one edge thereof. A link 9 has one end pivoted to the block, within the notch. This link passes centrally through the opening in lever 5, without connection therewith, and its lower end is pivotally connected with lever 6 at a location shown as midway between the ends thereof. Lever 5, previously identified as generally O-shaped, is seen at FIGURE 2 to have lugs 5a, 5b at one end to receive between them with a smooth fit, the contiguous end of link 4. The lugs are pierced with aligned holes to receive a bearing pin or axle, not shown. The sides of lever 5 are of I shape in transverse section to define a web and side flanges. The web is cut away at the central parts of the lever to form bearing openings 5c and 5d. At its other end the lever terminates in lugs 5e, 5 which are axially spaced to receive between them with a smooth fit, the contiguous end of link 8. Lever '5 is thus very strong but relatively light in weight and of minimum inertia for the strength required.

Referring to FIGURES 1 and 4, first and second bars 23 and 24 are each integrally fixed at one end with the under side of block 1, in vertically depending relation therefrom. At its lower end each 'bar has a cylindrical enlargement 25 and 2-6, which are pierced with aligned openings to receive bearing pins not shown by which each is pivotally connected to lever 5 within a respective one of the openings 50, 5d, on a common axis transversely of the lever. In the model shown this axis lies midway between the axis 20 by which lever 5 is pivoted to link 8, and the axis 27 by which it is pivotally connected with link 4.

FIGURE 3 shows lever 6 in plan, from which it is seen to have at one end a first pair of ears 6a, 6b which embrace lug 21 and by means of a pivot pin not shown, pivotally connect this end of the lever with frame 2. The other end of the lever has ears 6c, 6d, which are pierced the same as 6a and 6b to receive a pivot pin not shown, by which the lever is connected to link 8. All of the pivot axes between the links and levers, as just described, are parallel and parallel with the longitudinal axis of frame 2.

The link and lever assembly by which block 1' is connected with frame 2, is identical with the one just described, and each part of the second assembly, corresponding to a like part of the first assembly just described, is identified by a corresponding reference number primed. Thus it is sufiicient to identify bracket 7', link 4', lever 5', links 8', 9', lever 6' and bar 24 rigid with block 1. In FIGURE 1, bar 23 as well as the bar corresponding thereto integral with block 1', are obscured so that only a portion of bearing enlargements 25, 25' appear.

The link and lever construction thus provided applies the component forces necessary to move frame 2 in its orbital path, in the direction horizontal transverse to the frame. The component horizontal force effective to move the frame in the direction of its longitudinal axis is applied by blocks 1, 1', through a linkage as set forth in my prior copending application Ser. No. 463,248, filed June 11, 1965, now Patent No. 3,353,304 issued Nov. 21, 1967. This linkage comprises a bracket 16 previously mentioned, fixed centrally to frame 2 and having upstanding arms between which is pivoted a lever 11. This lever has aligned trunnions extending from its central portion and which are pivoted at 15 in the ends of the upstanding arms of bracket 16 so that the lever is pivotable about an axis parallel with frame 2 and, when the device is operating, parallel with the surface of the sheet of glass being worked or surfaced. A link 10 has one end pivotally connected to element 1 at 13, and its other end pivoted to the adjacent end of lever 11 at 10a. A second link 12 has one end pivoted to block 1 as indicated at 14 and its other end pivotally connected to the adjacent end of lever 11, as indicated at 10b.

As shown, the links and lever are preferably wide and ribbed for greater stiffness and rigidity. Links 10 and 12 are formed with forked ends. Referring to link 10, one forked end thereof embraces the contiguous end of lever 11 and a pivot pin, not shown, passes through aligned holes in the link and lever. Likewise the other forked end of link 10 embraces a pierced lug 1a integrally attached to one side edge of element 1, and a second pivot pin passes through aligned holes in the lug and link.

Link 12 is essentially like link 10 in shape, size and effective length. Its pivotal connection with lever 11 may be a duplicate of that interconnect-ing link 10 and lever 11. However, element 1 has a lug 1c upstanding from its top surface as viewed upon FIGURE 1, and adjacent and parallel with one side edge thereof. This lug is pierced and a pivot pin passes through and is secured in the aligned holes of the lug and forked end of the link. The construction and arrangement are such that blocks or elements 1 and 1 are normally coplanar despite a small angularity of lever 11 with respect to the plane of frame 2. Thus links 10 and 12 while normally essentially parallel with the plane of frame 2 are at slightly different elevations thereabove.

The linkage thus described resists twisting of frame 2 about a normally vertical axis, with respect to blocks 1 and 1', as well as about a normally horizontal axis parallel with the longitudinal axis of the frame, but permits limited vertical displacements between the frame and elements without, however, varying the relation between the effective lengths of the links, that is, their lengths projected upon the plane of frame 2 or, in operation, upon the plane of the sheet of glass being surfaced.

FIGURE 5 shows schematically one of the linkage assemblies of FIGURE 1, with a force diagram superposed thereon. In this figure the numerals 1 through 9 identify the same elements as have been previously described in connection with FIGURE 1, so that it is sufl'icient to mention block 1, rubbing pad frame 2, sheet of glass 3, links 4, 8 and 9, levers 5 and 6, bracket 7.

Assuming that at a certain moment block 1 exerts upon lever 5 a force having a horizontal component Fe moving the frame to the right as viewed in the figure, the force can be decomposed into a first or vertical component Fv and a second component Ft coincident with the longitudinal axis of inclined link 4, that is, a component acting along line A--B. Let E represent at this moment the resultant of forces acting through the inertia center I, necessary to overcome the inertia of the moving frame and parts connected therewith; and Fg the resultant of forces required to overcome the friction between the pad on frame 2 and the surface of sheet 3. The two resultant forces Pi and Fg are parallel and vertically spaced a short distance and can be represented by a single resultant Fi+Fg, acting through a point K located on the line through the inertia center I of the rubbing frame assembly, perpendicular to the rubbing surface, and between said inertia center I and the point of intersection of said perpendicular with the rubbing surface.

The parts are so constructed and arranged, as shown, so that the axis of link 4 extended or, what is the same thing, the line of action of force Ft, passes through point K. It is thus apparent that this force has no couple other- 5 wise tending to tilt frame 2 about any axis normal to the plane of FIGURE 4.

The force Ft has a vertical component Fv acting downwardly through point A, which point coincides with or lies upon the axis of pivotal connection between bracket 7 and link 4. This force Fv', of course, varies continuously with Fe and is thus undesirable because it would, unless annulled, correspondingly continuously vary the resultant effecting pressure of the rubbing pad upon the glass. The force Fv, however, has at each instant a value equal and opposite to Fv', and tends to elevate point B which lies on the axis of pivotal connection between link 4 and lever 5. Lever 5 tends to pivot about point C which lies on the fulcrum axis of the lever, or axis 28, FIGURE 2, so that its remote end D which, in turn, lies upon the axis of pivotal connection 20, FIGURES 1 and 2, between lever 5 and link 8 tends to move in an arcuate path about point C. A force is thus applied through link 8 to the end of lever 6 at point E, which lies upon the axis of pivotal connection between link 8 and lever 6. It will be recalled that lever 6 is pivoted between its ends on an axis defined by a bearing at the lower end of link 9 which is pivotally connected with block 1.

The downward force thus exerted upon lever 6 at point E, by link 8, tends to elevate the end of the lever pivotally attached at 21 to frame 2, and represented in the figure by point I. The relation between the lengths of levers 5, 6 and their pivot axes defined thereby is so chosen that there exists the linear relation CD GE the points being as indicated upon FIGURE 4. This relation is conveniently but not necessarily established by making BC=CD and EG GJ, as shown upon the figure.

The force Fc thus applied by lever 6 at point I combines with the force Ft to give a resultant Fe which is the force acting through point K. Thus all external force couples otherwise tending to tilt the frame 2 about an axis normal to the plane of FIGURE 4, are eliminated and R=Fe(Ft'+Fg) R being the force acting to move the frame 2 to the right as viewed upon the figure.

I have thus provided a mechanism which fulfills all of the objects stated and which effectively eliminates all couples otherwise acting upon the rubbing frame and which, unless annulled, tend to tilt the frame out of the plane of the sheet of glass. As a result the orbital movement of the frame is smooth and devoid of vibration or chatter with the result that there is produced a final finished surface upon the glass that is truly planar to a high degree of accuracy. It is to be particularly noted that the linkage 4 through 12 permits at all times the slight vertical displacement of frame 2 relatively to blocks 1 and 1, in the direction normal to the plane surface of the frame, without change in the angularity of link 4 or of lever 5. Hence such displacements such as those caused by wear upon the pad, removal of glass from the surfaces being worked, etc., have no effect upon the accuracy or operation of the invention.

While I have disclosed the form of the invention presently preferred by me, numerous alterations, modifications and substitutions of equivalents will occur to those skilled in the art, after a study of the foregoing disclosure. Hence the disclosure is to be taken in an illustrative rather than a limiting sense.

Having fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. The method of surfacing sheet glass by rubbing the same in an orbital path, comprising, applying to at least a point of the rubbing means, the driving force to move the same, said force having a first component parallel with the surface being rubbed, and a second component normal to said surface, and directing said force continuously through a point located on the line perpendicular to the rubbing surface and through the inertia center of the rubbing frame asembly, said point lying between said inertia center and the point of intersection of said perpendicular line with the rubbing surface.

2. The method of claim 1, and simultaneously generating and applying to the rubbing means, a component force through said inertia center, equal and opposite to said second component.

References Cited UNITED STATES PATENTS 2,955,389 10/1960 Thebault 51-119 2,984,051 5/1961 Monnet 51-119 3,263,376 8/1966 Walters 51283 HAROLD D. WHITEHEAD, Primary Examiner.

US. Cl. X.R. 

